1. Field
This invention relates to a technology for specifying a communication path in a specific area on a network divided into a plurality of areas.
2. Description of Related Art
An example of an Internet Protocol (IP) network is illustrated in FIG. 1. In this network, it is desired that a communication path on the network can be specified, for example, for the following purposes: (1) to check whether the communication path follows the design of the network; (2) to specify a path to be affected in case degradation in communication quality occurs; (3) to specify a path around which a maintenance worker needs to detour at a maintenance work.
For example, an Open Shortest Path Fast (OSPF) protocol is used in a routing control in the IP network. In the OSPF, respective network devices (for example, a router) exchange packets called Link State Advertisement (LSA) to generate and store a topology and a routing table.
There is a technology for specifying a communication path in a network which performs the routing through the OSPF by providing a monitoring server which captures packets flowing in the network to collect the LSA. FIG. 2 illustrates an example of the case of providing with the monitoring server. In FIG. 2, the monitoring server captures the packets flowing in a router e and generates and maintains the same topology and routing table as the router. For example, the path passing through a router g, a router b, a router c, a router d and a router i is specified as the communication path of the packet transmitted from “12.0.0.0/8” to “10.0.0.0/8”. In FIG. 2, the router g and the router i are the Autonomous System Boundary Routers (ASBRs).
Further, the network may be operated, divided into a plurality of areas, as illustrated in FIG. 3, in order to reduce the loads on the router in the OSPF. In FIG. 3, a router g and a router i are the ASBRs and a router a, a router b, a router d, and a router f are the area border routers (ABR: Area Border Router) (hereinafter, the area border router is referred to as an edge router). In this case, it may happen that the monitoring server connected to the backbone (Backbone) cannot obtain the detailed LSA about an area other than the area to which the server is connected (i.e. Area 1 and Area 2). In FIG. 3, the packets transmitted from “12.0.0.0/8” to “10.0.0.0/8” pass through the router a or the router b. The edge router which receives packets from a router in a neighboring area is referred to as an input edge router. When the monitoring server cannot obtain the detailed LSA about the Area 1, the communication path in the Area 1 is left unspecified, consequently, the edge router which receives the packets cannot be specified. Therefore, the monitoring server cannot specify the input edge router and, as a result, the monitoring server cannot specify the communication path in the Backbone. In this case, it is necessary to provide another monitoring server on the Area 1 which is not monitored, in order to specify the communication path in the Backbone.